Supported organic catalyst systems, particularly metallocene catalyst systems, are of interest for use in polymerization reactions. These catalyst systems typically contain one or more metallocene compounds on a porous support media, such as silica. Supporting the metallocene compounds in this manner improves the handling characteristics of the polymer product and gives better control of reaction rates.
Typically, the supported systems have heretofore been formed by dissolving the catalyst compounds in solvent and attempting to permeate the pores of the support with catalyst solution to form a uniform film of catalyst on the support. For example, U.S. Pat. Nos. 5,665,665 and 5,721,184 disclose the use of toluene to dissolve and transfer metallocene catalyst to the surface of a support material.
The present inventors have come to appreciate that such prior processes are disadvantageous for several reasons. One such disadvantage is that the prior art methods result in relatively uneven distribution of the catalyst on the support. It is believed that this uneven distribution results from non-uniform evaporation of the solvent, which produces concentration gradients and creates uneven layers on the support. This uneven deposition can lead to fouling of the reactor in which the catalyst is used. In addition, the present inventors have come to realize that the use of solvents having relatively high surface tension inhibits penetration of the solution into the fine pores on a support. We have also come to appreciate that the solvents used in the prior art processes require excessive energy and time to remove, and that many solvents used in the prior art processes are disadvantageously flammable.
Recognizing these and other drawbacks of the prior art, the present inventors have perceived a need for a new, efficient and more desirable method for producing a wide range of supported organic catalyst systems. These and other objects are achieved by the present invention as described below.